Exocyclic C-C Modifications of Aromatic Polyketides

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DESCRIPTION (provided by applicant): Aromatic polyketides differ from other polyketides by their characteristic polycyclic aromatic structures. These polyketides are widely distributed in bacteria, fungi and plants, and many of them are clinically valuable agents (e.g. tetracyclines, daunorubicin) or exhibit other fascinating biological activities. While the fundamental biosynthetic principles of aromatic polyketides has been extensively explored, little is known regarding the construction of many existing unique exocyclic carbon-carbon (C-C) attachments to these metabolites. The current proposal is designed to expand our understanding of this phenomenon by bringing together the study of two naturally occurring novel aromatic polyketide systems, which promise access to three distinct exocyclic aromatic polyketide C-C modifications. The first, hedamycin from Streptomyces griseoruber, offers one of the only naturally occurring di-C-glycosylation events as well as an additional type I PKS-directed C-alkyl chain substitution of the polycyclic ring system. The second, dynemicin from Micromonospora chersina, offers the only known naturally occurring fusion between an enediyne and aromatic polyketide. The intended studies are expected to lay a foundation to understand the unique mechanisms of these processes and also the potential to utilize these tools for combinatorial biosynthesis toward novel therapeutics. The first phase of this massive project is specifically intended to i) provide the necessary genetic tools and information to form reasonable mechanistic hypotheses for all three events, ii) to initiate in vivo and in vitro experiments explicitly designed to address the C-glycosylation and C-alkylation stages of hedamycin/pluramycin biosynthesis and Hi) attempt to combine aspects of all three aromatic C-C modification systems toward enhancing the diversification of aromatic polyketide structures. A particular focus of the final diversification strategies presented will be focused upon conjugation of these highly reactive antitumor antibiotics with known tumor-directing peptides.